Here's a pretty infographic from Karten Design detailing the information:

Another interesting stat in there is that 5 billion people have access to a mobile phone, which represents 72% of the world's population. Now that is accessibility!

If you're currently considering purchasing a content authoring tool, a learning management system or another online software product, it makes it all the more important to ask the vendor questions about their current and future plans for mobile. With the mobile learning industry having grown $326M in 2010 over 2009, it would be a mistake not to consider how your content is going to perform on mobile devices.